372 lines
12 KiB
Groff
372 lines
12 KiB
Groff
'\" t
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.\" Title: passwd
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.\" Author: Julianne Frances Haugh
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.\" Generator: DocBook XSL Stylesheets vsnapshot <http://docbook.sf.net/>
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.\" Date: 2026-02-01
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.\" Manual: User Commands
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.\" Source: shadow-utils 4.19.3
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.\" Language: Chinese Simplified
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.\"
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.TH "PASSWD" "1" "2026-02-01" "shadow\-utils 4\&.19\&.3" "User Commands"
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.\" -----------------------------------------------------------------
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.\" * Define some portability stuff
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.\" -----------------------------------------------------------------
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.\" ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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.\" http://bugs.debian.org/507673
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.\" http://lists.gnu.org/archive/html/groff/2009-02/msg00013.html
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.\" ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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.ie \n(.g .ds Aq \(aq
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.el .ds Aq '
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.\" -----------------------------------------------------------------
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.\" * set default formatting
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.\" -----------------------------------------------------------------
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.\" disable hyphenation
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.nh
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.\" disable justification (adjust text to left margin only)
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.ad l
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.\" -----------------------------------------------------------------
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.\" * MAIN CONTENT STARTS HERE *
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.\" -----------------------------------------------------------------
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.SH "名称"
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passwd \- 更改用户密码
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.SH "大纲"
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.HP \w'\fBpasswd\fR\ 'u
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\fBpasswd\fR [\fIoptions\fR] [\fILOGIN\fR]
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.SH "描述"
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.PP
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The
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\fBpasswd\fR
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command changes passwords for user accounts\&. A regular user can only change the password for their own account, while the superuser can change the password for any account\&. The
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\fBpasswd\fR
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also changes the account or associated password validity period\&.
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.SS "密码更改"
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.PP
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If the account has a non\-empty password, the user is first prompted to enter their current password\&. The entered password is encrypted and compared to the stored value\&. The user has only one attempt to enter the correct password\&. The superuser can bypass this step to allow changing forgotten passwords\&.
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.PP
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After the password has been entered, password aging information is checked to determine if the user is permitted to change the password at this time\&. If not,
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\fBpasswd\fR
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refuses to change the password and exits\&.
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.PP
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The user is then prompted twice for a replacement password\&. The second entry is compared against the first and both are required to match for the password to be changed\&.
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.PP
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Then, the password is tested for complexity\&.
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\fBpasswd\fR
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rejects passwords that do not meet the complexity requirements\&. Do not include the system default erase or kill characters\&.
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.SS "关于用户密码的提示"
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.PP
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The security of a password depends on the strength of the encryption algorithm and the size of the key space\&. The legacy
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\fIUNIX\fR
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System encryption method is based on the NBS DES algorithm\&. More recent methods are now recommended (see
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\fBENCRYPT_METHOD\fR)\&. The size of the key space depends on the randomness of the selected password\&.
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.PP
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Compromises in password security normally result from careless password selection or handling\&. For this reason, you should not select a password which appears in a dictionary or one that must be written down\&. The password should also not be a proper name, your license number, birth date, or street address\&. Any of these may be used as guesses to violate system security\&.
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.PP
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As a general guideline, passwords should be long and random\&. It\*(Aqs fine to use simple character sets, such as passwords consisting only of lowercase letters, if that helps memorizing longer passwords\&. For a password consisting only of lowercase English letters randomly chosen, and a length of 32, there are 26^32 (approximately 2^150) different possible combinations\&. Being an exponential equation, it\*(Aqs apparent that the exponent (the length) is more important than the base (the size of the character set)\&.
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.PP
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You can find advice on how to choose a strong password on https://en\&.wikipedia\&.org/wiki/Password_strength
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.SH "选项"
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.PP
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The options which apply to the
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\fBpasswd\fR
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command are:
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.PP
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\fB\-a\fR, \fB\-\-all\fR
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.RS 4
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This option can be used only with
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\fB\-S\fR
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and causes show status for all users\&.
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.RE
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.PP
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\fB\-d\fR, \fB\-\-delete\fR
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.RS 4
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Deletes a user\*(Aqs password, making it empty\&. This command sets the account to be passwordless\&.
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.RE
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.PP
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\fB\-e\fR, \fB\-\-expire\fR
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.RS 4
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让一个账户的密码立即过期。这可以强制一个用户下次登录时更改密码。
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.RE
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.PP
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\fB\-h\fR, \fB\-\-help\fR
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.RS 4
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显示帮助信息并退出。
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.RE
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.PP
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\fB\-i\fR, \fB\-\-inactive\fR\ \&\fIINACTIVE\fR
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.RS 4
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This option is used to disable an account after the password has been expired for a number of days\&. After a user account has had an expired password for
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\fIINACTIVE\fR
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days, the user may no longer sign on to the account\&.
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.RE
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.PP
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\fB\-k\fR, \fB\-\-keep\-tokens\fR
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.RS 4
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表示密码更改只应该因为认证口令(密码)过期更改。用户希望保持他们尚未过期的口令。
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.RE
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.PP
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\fB\-l\fR, \fB\-\-lock\fR
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.RS 4
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锁定指定账户的密码。此选项通过将密码更改为一个不可能与加密值匹配的值来禁用(它在密码开头添加一个\(lq!\(rq)。
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.sp
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Note that this does not disable the account\&. The user may still be able to login using another authentication token (e\&.g\&. an SSH key)\&. To disable the account, administrators should use
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\fBusermod \-\-expiredate 1\fR
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(this sets the account\*(Aqs expire date to 1970\-01\-02)\&.
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.sp
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被锁定了密码的用户不允许更改密码。
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.RE
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.PP
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\fB\-n\fR, \fB\-\-mindays\fR\ \&\fIMIN_DAYS\fR
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.RS 4
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Set the minimum number of days between password changes to
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\fIMIN_DAYS\fR\&. A value of zero for this field indicates that the user may change their password at any time\&.
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.RE
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.PP
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\fB\-q\fR, \fB\-\-quiet\fR
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.RS 4
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安静模式。
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.RE
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.PP
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\fB\-r\fR, \fB\-\-repository\fR\ \&\fIREPOSITORY\fR
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.RS 4
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change password in
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\fIREPOSITORY\fR
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repository
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.RE
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.PP
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\fB\-R\fR, \fB\-\-root\fR\ \&\fICHROOT_DIR\fR
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.RS 4
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Apply changes in the
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\fICHROOT_DIR\fR
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directory and use the configuration files from the
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\fICHROOT_DIR\fR
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directory\&. Only absolute paths are supported\&. No SELINUX support\&.
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.RE
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.PP
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\fB\-P\fR, \fB\-\-prefix\fR\ \&\fIPREFIX_DIR\fR
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.RS 4
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Apply changes to configuration files under the root filesystem found under the directory
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\fIPREFIX_DIR\fR\&. This option does not chroot and is intended for preparing a cross\-compilation target\&. Some limitations: NIS and LDAP users/groups are not verified\&. No PAM support\&. No SELINUX support\&.
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.RE
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.PP
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\fB\-S\fR, \fB\-\-status\fR
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.RS 4
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显示账户状态信息。状态信息包含 7 个字段。首个字段是用户的登录名，第二个字段表示用户账户是否已经锁定密码(L)、没有密码 (NP)或者密码可用(P)，第三个字段给出最后一次更改密码的日期。接下来的四个字段分别是密码的最小年龄、最大年龄、警告期和禁用期。这些年龄以天为单位计算。
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.RE
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.PP
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\fB\-u\fR, \fB\-\-unlock\fR
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.RS 4
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Unlock the password of the named account\&. This option re\-enables a password by changing the password back to its previous value (to the value before using the
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\fB\-l\fR
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option)\&.
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.RE
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.PP
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\fB\-w\fR, \fB\-\-warndays\fR\ \&\fIWARN_DAYS\fR
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.RS 4
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Set the number of days of warning before a password change is required\&. The
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\fIWARN_DAYS\fR
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option is the number of days prior to password expiration during which the user is warned that their password is about to expire\&.
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.RE
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.PP
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\fB\-x\fR, \fB\-\-maxdays\fR\ \&\fIMAX_DAYS\fR
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.RS 4
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Set the maximum number of days a password remains valid\&. After
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\fIMAX_DAYS\fR, the password is required to be changed\&.
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.sp
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Passing the number
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\fI\-1\fR
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as
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\fIMAX_DAYS\fR
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will remove checking a password\*(Aqs validity\&.
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.RE
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.PP
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\fB\-s\fR, \fB\-\-stdin\fR
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.RS 4
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This option is used to indicate that passwd should read the new password from standard input, which can be a pipe\&.
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.RE
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.SH "CAVEATS"
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.PP
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密码复杂性检查在每台机器间不同。用户应该选择适合的尽量复杂的密码。
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.PP
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在启动了 NIS 的系统上，如果没有登录 NIS 服务器，用户或许不能更改自己的密码。
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.SH "配置文件"
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.PP
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The following configuration variables in
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/etc/login\&.defs
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change the behavior of this tool:
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.PP
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\fBENCRYPT_METHOD\fR (string)
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.RS 4
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This defines the system default encryption algorithm for encrypting passwords (if no algorithm is specified on the command line)\&.
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.sp
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It can take one of these values:
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\fIDES\fR
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(default),
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\fIMD5\fR, \fISHA256\fR, \fISHA512\fR\&. MD5 and DES should not be used for new hashes, see
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crypt(5)
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for recommendations\&.
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.sp
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Note: this parameter overrides the
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\fBMD5_CRYPT_ENAB\fR
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variable\&.
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.RE
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.PP
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\fBMD5_CRYPT_ENAB\fR (boolean)
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.RS 4
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Indicate if passwords must be encrypted using the MD5\-based algorithm\&. If set to
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\fIyes\fR, new passwords will be encrypted using the MD5\-based algorithm compatible with the one used by recent releases of FreeBSD\&. It supports passwords of unlimited length and longer salt strings\&. Set to
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\fIno\fR
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if you need to copy encrypted passwords to other systems which don\*(Aqt understand the new algorithm\&. Default is
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\fIno\fR\&.
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.sp
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This variable is superseded by the
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\fBENCRYPT_METHOD\fR
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variable or by any command line option used to configure the encryption algorithm\&.
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.sp
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This variable is deprecated\&. You should use
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\fBENCRYPT_METHOD\fR\&.
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.RE
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.PP
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\fBOBSCURE_CHECKS_ENAB\fR (boolean)
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.RS 4
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Enable additional checks upon password changes\&.
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.RE
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.PP
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\fBPASS_ALWAYS_WARN\fR (boolean)
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.RS 4
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Warn about weak passwords (but still allow them) if you are root\&.
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.RE
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.PP
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\fBPASS_CHANGE_TRIES\fR (number)
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.RS 4
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Maximum number of attempts to change password if rejected (too easy)\&.
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.RE
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.PP
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\fBPASS_MAX_LEN\fR (number), \fBPASS_MIN_LEN\fR (number)
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.RS 4
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Number of significant characters in the password for crypt()\&.
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.sp
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\fBPASS_MAX_LEN\fR
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is 8 by default\&. Don\*(Aqt change unless your crypt() is better\&.
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.sp
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\fBPASS_MAX_LEN\fR
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is only used for DES\&. It is ignored if an encryption algorithm other than DES is used, either because
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\fBMD5_CRYPT_ENAB\fR
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set to
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\fIyes\fR
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or
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\fBENCRYPT_METHOD\fR
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set to an algorithm other than
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\fIDES\fR\&.
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.sp
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In addition,
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\fBPASS_MAX_LEN\fR
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is only used if
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\fBOBSCURE_CHECKS_ENAB\fR
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set to
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\fIyes\fR\&.
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.sp
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Note: This only affects the generation of user passwords\&. Group password lengths are not checked\&.
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.RE
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.PP
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\fBSHA_CRYPT_MIN_ROUNDS\fR (number), \fBSHA_CRYPT_MAX_ROUNDS\fR (number)
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.RS 4
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When
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\fBENCRYPT_METHOD\fR
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is set to
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\fISHA256\fR
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or
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\fISHA512\fR, this defines the number of SHA rounds used by the encryption algorithm by default (when the number of rounds is not specified on the command line)\&.
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.sp
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With a lot of rounds, it is more difficult to brute force the password\&. But note also that more CPU resources will be needed to authenticate users\&.
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.sp
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If not specified, the libc will choose the default number of rounds (5000), which is orders of magnitude too low for modern hardware\&.
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.sp
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The values must be inside the 1000\-999,999,999 range\&.
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.sp
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If only one of the
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\fBSHA_CRYPT_MIN_ROUNDS\fR
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or
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\fBSHA_CRYPT_MAX_ROUNDS\fR
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values is set, then this value will be used\&.
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.sp
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If
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\fBSHA_CRYPT_MIN_ROUNDS\fR
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>
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\fBSHA_CRYPT_MAX_ROUNDS\fR, the highest value will be used\&.
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.RE
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.SH "文件"
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.PP
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/etc/passwd
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.RS 4
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用户账户信息。
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.RE
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.PP
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/etc/shadow
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.RS 4
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安全用户账户信息。
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.RE
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.PP
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/etc/login\&.defs
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.RS 4
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Shadow 密码套件配置。
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.RE
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.SH "退出值"
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.PP
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The
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\fBpasswd\fR
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command exits with the following values:
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.PP
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\fI0\fR
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.RS 4
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success
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.RE
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.PP
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\fI1\fR
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.RS 4
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permission denied
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.RE
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.PP
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\fI2\fR
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.RS 4
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invalid combination of options
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.RE
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.PP
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\fI3\fR
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.RS 4
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unexpected failure, nothing done
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.RE
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.PP
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\fI4\fR
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.RS 4
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unexpected failure,
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passwd
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file missing
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.RE
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.PP
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\fI5\fR
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.RS 4
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passwd
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file busy, try again
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.RE
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.PP
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\fI6\fR
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.RS 4
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invalid argument to option
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.RE
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.PP
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\fI10\fR
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.RS 4
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an error was returned by
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pam(3)
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.RE
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.SH "参见"
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.PP
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\fBchpasswd\fR(8),
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\fBmakepasswd\fR(1),
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\fBpasswd\fR(5),
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\fBshadow\fR(5),
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\fBlogin.defs\fR(5),
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\fBusermod\fR(8)\&.
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.PP
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The following web page comically (yet correctly) compares the strength of two different methods for choosing a password: "https://xkcd\&.com/936/"
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